Atomic Magnetometer System

Abstract

To monitor precession of alkali metal vapor by monitoring a detection beam corresponding to an optical probe beam exiting a sensor cell.SOLUTION: A magnetometer 50 includes: a sensor cell 58 that includes alkali metal vapor; and a magnetic field generator system that generates prescribed AC magnetic fields via the sensor cell 58. The magnetometer 50 includes a laser system that is configured to supply optical pump and probe beams via the sensor cell in a pulsed manner for facilitating precession of the alkali metal vapor, and to supply a detection beam corresponding to the optical probe beam exiting the sensor cell 58, in which the detection beam exhibits an optical property corresponding to modified precession of the alkali metal vapor based on a plurality of prescribed AC magnetic fields and an external magnetic field. The magnetometer 50 further includes a detection system to monitor the detection beam to thereby detect the modified precession of the alkali metal vapor, and to calculate scalar and vector components of the external magnetic field on the basis of the plurality of prescribed AC magnetic fields.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure generally relates to sensor systems, and more particularly to atomic magnetometers.

Background Art

[0002] Magnetometer systems such as nuclear magnetic resonance (NMR) magnetometers and / or electron paramagnetic resonance (EPR) magnetometers may include cells containing one or more alkali metal vapors, such as rubidium or cesium, that can exhibit precession motion characteristics in response to an external magnetic field. Thus, a magnetometer system may be configured to detect an external magnetic field based on the precession motion characteristics of the alkali metal vapor. A typical magnetometer system that realizes detection of an external magnetic field on three vector axes uses a combination of multiple uniaxial or biaxial vector systems. Such magnetometer systems may typically exhibit sensitivity to dynamics or system misalignment that can cause inaccuracies when attempting to determine an all-field scalar measurement. Thus, all-field scalar magnetometer systems are often utilized when high sensitivity and stability are required in a dynamic environment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] One embodiment includes a magnetometer that includes a sensor cell containing an alkali metal vapor and a magnetic field generator system that generates a predetermined AC magnetic field through the sensor cell. The magnetometer also includes a laser system configured to pulse a light pump beam and a light probe beam through the sensor cell to facilitate the precession motion of the alkali metal vapor and to supply a detection beam corresponding to the light probe beam exiting the sensor cell. The detection beam exhibits optical properties corresponding to the altered precession motion of the alkali metal vapor based on the predetermined AC magnetic field and an external magnetic field. The magnetometer also includes a detection system that monitors the detection beam to detect the altered precession motion of the alkali metal vapor and calculates a scalar component and a vector component of the external magnetic field based on the plurality of predetermined AC magnetic fields.

[0005] Another embodiment includes a method for measuring a scalar component and a vector component of an external magnetic field via a magnetometer system. The method includes providing a plurality of predetermined AC magnetic fields through a sensor cell associated with the magnetometer. The sensor cell contains an alkali metal vapor. The method also includes pulsing a light probe beam and a light pump beam through the sensor cell and determining a total magnetic field that includes the external magnetic field and each of the plurality of predetermined AC magnetic fields in response to receiving a detection beam corresponding to the light probe beam exiting the sensor cell. The method further includes demodulating the total magnetic field based on the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field.

[0006] Another embodiment includes a plurality of magnetometers. Each of the plurality of magnetometers includes a sensor cell containing an alkali metal vapor, a magnetic field generator system configured to generate a plurality of predetermined AC magnetic fields through the sensor cell, and a laser system configured to pulse a light pump beam and a light probe beam through the sensor cell to promote the precession motion of the alkali metal vapor and to supply a detection beam corresponding to the light probe beam exiting the sensor cell, wherein the detection beam exhibits optical characteristics corresponding to the modified precession motion of the alkali metal vapor based on the plurality of predetermined AC magnetic fields and an external magnetic field, and a detection system configured to monitor the detection beam to detect the modified precession motion of the alkali metal vapor and to calculate a scalar component and a vector component of the external magnetic field based on the plurality of predetermined AC magnetic fields. The system further includes a magnetic field tensor processor configured to calculate a magnetic field gradient based on the scalar component and the vector component of the external magnetic field calculated by each of the plurality of magnetometers.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0008] The present disclosure generally relates to sensor systems, and more specifically to atomic magnetometer systems. The magnetometer system may include an array of magnetometers. Each magnetometer is configured as a Synchronous Light-pulse Atomic Magnetometer (SLAM) that includes a simultaneous pump / pulse beam pumping and monitoring method similar to a Bell-Bloom all-optical magnetometer. The magnetometer system includes a laser system that includes at least one pump laser configured to generate at least one optical pump beam and at least one probe laser configured to generate at least one optical probe beam. As an example, the pump beam and the optical probe beam may be coupled via an optical coupler (e.g., a 2×2 optical coupler) and provided collinearly. The pump beam and the optical probe beam are provided via a sensor cell that includes an alkali metal vapor. The alkali metal vapor may precess in response to an external magnetic field based on the alignment of the net magnetic moment of the alkali metal vapor in the cell in response to the circularly polarized optical pump beam. As a result of this precession, the linearly polarized optical probe beam may exhibit a Faraday rotation as it passes through the sensor cell. This Faraday rotation is based on the instantaneous orientation of the net magnetic moment of the alkali metal vapor as the alkali metal vapor precesses. Thus, by monitoring the detection beam corresponding to the optical probe beam exiting the sensor cell, the precession of the alkali metal vapor can be monitored.

[0009] As an example, the monitoring results of the precession of the alkali metal vapor can be provided as feedback to a timing controller that generates a timing signal. Thus, the timing signal can be supplied to the laser system to provide a timing reference regarding when to supply the pulsed optical pump beam and the optical probe beam through the sensor cell. For example, the laser system can supply an optical pump beam pulse through the sensor cell in response to the timing signal to pump the alkali metal vapor once per period of precession (e.g., when the magnetic moment is aligned approximately parallel to the optical pump beam axis). As another example, the laser system can supply an optical probe beam pulse through the sensor cell in response to the timing signal when the magnetic moment of the alkali metal vapor is approximately parallel and antiparallel to the optical probe beam axis to calibrate the magnetometer system. Also, the laser system can supply an optical probe beam pulse through the sensor cell in response to the timing signal when the magnetic moment of the alkali metal vapor is approximately orthogonal to the optical probe beam axis to monitor the amplitude and direction of the external magnetic field as indicated by the Faraday rotation of linearly polarized light.

[0010] Also, each magnetometer can be used to calculate the magnitude of the vector of the external magnetic field. For example, an atomic magnetometer system can include a magnetic field system including a plurality of magnetic field generators each configured to generate a predetermined AC magnetic field along a predetermined axis through a sensor cell of each magnetometer. As an example, the magnetic field can be provided as three orthogonal magnetic fields each having an individual frequency. The square of the total magnetic field measured by each magnetometer is equal to the sum of each vector term, and each vector term is the square of the sum of the vector components of the corresponding magnetic field among the external magnetic field and the predetermined magnetic field. Accordingly, the detection system is configured to square the measured total magnetic field and demodulate the squared total magnetic field by first and second harmonics related to the predetermined AC magnetic field to calculate the scalar component and the vector component of the external magnetic field. Also, by comparing the scalar component and the vector component of the external magnetic field measured by each magnetometer in the array, the atomic magnetometer system can operate as a tensor system for determining the magnetic field gradient of the external magnetic field.

[0011] FIG. 1 shows an example of a magnetometer system 10. The magnetometer system 10 can be implemented for any of various applications for measuring an external magnetic field, such as navigation. For example, the magnetometer system 10 can be implemented in an inertial navigation system (INS) in an aircraft or a spacecraft to assist in real-time navigation or positioning. As described herein, the magnetometer system 10 can be implemented to measure the scalar component and the vector component of the external magnetic field and determine the magnetic field gradient related to the external magnetic field.

[0012] The magnetometer system 10 includes a magnetometer array 12 that includes a plurality (N) of magnetometers 14, where N is a positive integer greater than 1. As an example, each magnetometer 14 can be configured as an atomic magnetometer (e.g., Synchronous Light-pulse Atomic Magnetometers (SLAM)) each configured to individually measure an external magnetic field. As will be described in detail herein, each magnetometer 14 includes a sensor cell through which an external magnetic field is provided for measurement. The magnetometer system 10 also includes a magnetic field system 16 that includes a plurality (X) of magnetic field generators 18, where X is a positive integer greater than 1. In the example of FIG. 1, each magnetic field generator 18 is configured to generate a predetermined AC magnetic field indicated by B1 to B X and is configured to generate a predetermined AC magnetic field. Each of the predetermined AC magnetic fields B1 to B X is provided through the sensor cell of each magnetometer 14 of the magnetometer array 12.

[0013] For example, each magnetometer 14 can be used to calculate the magnitude of the vector of the external magnetic field. As an example, each of the predetermined AC magnetic fields B1 to B X generated by the magnetic field generator 18 can be provided along a predetermined axis through the sensor cell of each magnetometer 14. As an example, the magnetic fields B1 to B X can be provided as three orthogonal magnetic fields provided along the X, Y, and Z orthogonal axes. Also, each of the magnetic fields B1 to B X has an individual frequency unique to each other. Thus, as will be described in detail herein, each magnetometer 14 can be configured to demodulate the total measured magnetic field by a predetermined AC magnetic field to determine the vector components of the external magnetic field.

[0014] In the example of FIG. 1, each magnetometer 14 is configured to generate a measured value of the external magnetic field indicated by B T1 to B TN . The measured values B T1 to B TN can include, for example, scalar and vector components of the external magnetic field. The measured values B T1 to B TNis supplied to a magnetic field tensor processor 20 configured to process measurement values B T1 ~B TN with respect to the physical position of the magnetometer 14 in three-dimensional space. For this reason, the magnetic field tensor processor 20 can be configured to determine a magnetic field gradient associated with the external magnetic field by comparing scalar components and / or vector components of the amplitude of the external magnetic field with respect to the physical position of the magnetometer 14 in three-dimensional space. Therefore, in addition to the magnetometer sensor for facilitating the measurement of the external magnetic field, the magnetic field tensor processor 20 can facilitate the use of the atomic magnetometer system 10 as a tensor sensor.

[0015] FIG. 2 shows an example of the magnetometer 50. The magnetometer 50 may correspond to one of the plurality of magnetometers 14 within the magnetometer array 12 in the example of FIG. 1. Therefore, in the following description of the example of FIG. 2, reference is made to the example of FIG. 1.

[0016] The magnetometer system 50 includes a pump laser 52 and a probe laser 54. The pump laser 52 is configured to generate an optical pump beam OPT PMP and the probe laser 54 is configured to generate an optical probe beam OPT PRB The optical pump beam OPT PMP and the optical probe beam OPT PRB are combined by a beam combiner 56. As an example, the beam combiner 56 can be configured as a 2×2 optical combiner (as opposed to, for example, a 2×1 optical combiner that may exhibit a 3 dB loss) to provide high power efficiency optical coupling. The beam combiner 56 is shown as providing a combined beam axis as shown as OPT CMB in the example of FIG. 2. The combined beam axis OPT CMB may correspond to a coaxial coupling of the optical pump beam OPT PMP and the optical probe beam OPT PRB Note that the optical pump beam OPT PMP and the optical probe beam OPT PRB are not necessarily on the combined beam axis OPT CMBThey do not have to be provided simultaneously as a single optical axis, but may simply share an optical axis.

[0017] In the example of Figure 2, OPT CMB The combined beam axis, shown as , is provided to pass through a sensor cell 58 containing alkali metal vapor therein. PMP can be provided through the sensor cell 58 to promote precession of the alkali metal vapor within the sensor cell 58 in response to an external magnetic field. Thus, an optical pump beam OPT PMP is the optical pump beam OPT PMP The magnetic moment of the alkali metal vapor can be aligned approximately parallel to the external magnetic field. Thus, the alkali metal vapor can precess about the external magnetic field based on the alignment of the magnetic moment of the alkali metal vapor, as described in detail herein.

[0018] In the example of FIG. 2, a dichroic mirror 60 is shown opposite the sensor cell 58, which mirrors the optical pump beam OPT PMP While stopping the optical probe beam OPT that has passed through the sensor cell 58, PRB Detection beam OPT corresponding to DET The optical detector 62 detects the detected beam OPT DET Based on this, the optical probe beam OPT passes through the sensor cell 58. PRB The optical detector 62 may be configured to detect the Faraday rotation of the optical detector 62. The optical detector 62 may provide a detection signal DET to the detection processor 64. In response to the detection signal DET, the detection processor 64 may generate scalar and vector components of the external magnetic field, denoted as a measurement BT, as described herein.

[0019] In the example of FIG. 2, the sensor cell 58 detects predetermined AC magnetic fields B1 to B X The detection processor 64 is also shown receiving predetermined AC magnetic fields B1-B XIt can be programmed using each frequency and vector orientation. As a result, the detection processor 64 can utilize the relationship between the squares of the vector components of the total magnetic field measured via the sensor cell 58. For example, the square of the total magnetic field measured by the detection processor 64 can be made equal to the sum of the orthogonal vector terms of the magnetic field, as described below, and each orthogonal vector term is the square of the sum of the vector components of the external magnetic field and the corresponding magnetic field among the predetermined magnetic fields B1 to B X can be the square of the sum of the vector components of the corresponding magnetic field among them.

[0020] B TOT 2 =B X 2 +B Y 2 +B Z 2 …(Equation 1) Here, B TOT is the total magnetic field measured via the sensor cell 58, B X is the sum of the X-axis component of the external magnetic field and at least one X-axis component of a predetermined AC magnetic field (for example, a predetermined AC magnetic field provided along the X-axis), B Y is the sum of the Y-axis component of the external magnetic field and at least one Y-axis component of a predetermined AC magnetic field (for example, a predetermined AC magnetic field provided along the Y-axis), B Z is the sum of the Z-axis component of the external magnetic field and at least one Z-axis component of a predetermined AC magnetic field (for example, a predetermined AC magnetic field provided along the Z-axis).

[0021] Therefore, the detection processor 64 is configured to square the measured total magnetic field B TOT and demodulate this squared total magnetic field B TOT 2 by the first and second harmonics related to the predetermined AC magnetic fields B1 to B X to calculate the scalar and vector components of the external magnetic field. For example, the individual total vector components B i can be calculated as follows.

[0022]

Number

[0023] Also, the detection processor 64 can generate and adjust the timing reference TIME provided to the timing controller 66 for using the pulse timing of the optical pump beam OPT PMP . The timing controller 66 can generate the timing signal TMR PMP supplied to the pump laser 52 to indicate the activation timing of the pulse of the optical pump beam OPT PMP . Similarly, the timing controller 66 can generate the timing signal TMR PRB supplied to the probe laser 54 to indicate the activation timing of the pulse of the optical probe beam OPT PRB . Therefore, the magnetometer 50 can operate as SLAM in the same manner as described in U.S. Patent Application Publication No. 2018 / 0348313, which is hereby incorporated by reference in its entirety.

[0024] As described above, the magnetometer 14 is arranged in a predetermined physical array within the magnetometer array 12, and the magnetic field tensor processor 20 can calculate the magnetic field gradient related to the external magnetic field based on the predetermined physical arrangement. FIG. 3 shows an example of the magnetometer array 100. The magnetometer array 100 may correspond to the magnetometer array 12 in the example of FIG. 1. Therefore, in the following description of the example of FIG. 3, the examples of FIGS. 1 and 2 are referred to.

[0025] The magnetometer array 100 includes a plurality of magnetometers shown as magnetometers 102, 104, 106, 108. Each magnetometer 102, 104, 106, 108 can be configured substantially the same as the magnetometers 14 and 50 in the respective examples of FIGS. 1 and 2. Thus, each magnetometer 102, 104, 106, 108 is configured to calculate the scalar component and the vector component of the external magnetic field, for example, based on demodulating the square of the total measured magnetic field by the primary and secondary harmonics of a predetermined AC magnetic field B1 to B X of.

[0026] In the example of FIG. 3, the magnetometers 102, 104, 106, 108 are arranged in a three-dimensional geometric array. In the example of FIG. 3, the three-dimensional geometric array is shown as an equilateral pyramid such that each magnetometer 102, 104, 106, 108 is equidistant from each other, as indicated by dotted lines 110 of approximately equal length. For example, the magnetometers 102, 104, 106 are arranged in a first planar array, the magnetometers 102, 104, 108 are arranged in a second planar array, the magnetometers 102, 106, 108 are arranged in a third planar array, and the magnetometers 104, 106, 108 are arranged in a fourth planar array. Thus, the magnetic field gradient related to the external magnetic field is based on the difference in the scalar component and / or the vector component of the external magnetic field measured by each magnetometer 102, 104, 106, 108 (for example, when N = 4, similar to that described in the example of FIG. 1, the measured values B T1 to B T4 ).

[0027] As an example, the magnetic field gradient of the external magnetic field can be determined from one of the planar arrays, and those of the magnetometers 102, 104, 106, 108 that deviate from that plane are implemented as redundant sensors to provide calibration of the atomic magnetometer system 10 and / or to provide a magnetic field gradient along the normal axis with respect to the corresponding planar array where the magnetic field gradient is measured. Thus, although the three-dimensional geometric array is shown as an equilateral pyramid, various other types of three-dimensional geometric arrays are possible. For example, three of the magnetometers 102, 104, 106, 108 can be arranged in a linear array, and the fourth of the magnetometers 102, 104, 106, 108 can be arranged obliquely with respect to the linear array. Other planar arrays and other out-of-plane arrangements of the magnetometers 102, 104, 106, 108 are also possible. Also, the magnetometer array 100 is not limited to four magnetometers and can include more or fewer magnetometers than the four magnetometers 102, 104, 106, 108. Thus, the magnetometer array can be arranged in any of a variety of ways.

[0028] As another example, the magnetometers of the magnetometer array 12 can be arranged in a more complex array to measure higher-order gradients. For example, by arranging a planar array of magnetometers 14, higher-order gradients can be measured. As an example, one such arrangement can include an array that includes a hexagonal arrangement of magnetometers 14. In this case, by including one magnetometer 14 at the center of the hexagonal arrangement, a circularly symmetric array of equilateral triangle groups is effectively provided where each equilateral triangle shares the central magnetometer 14 as a vertex. Such an arrangement enables measurement of a second-order tensor including measurement of all second-order gradients in addition to linear gradients, vector components, and scalar magnitudes.

[0029] The method according to various aspects of the present invention, taking into account the structural and functional features described above, can be further understood by referring to FIG. 4. For the sake of simplicity of explanation, the method of FIG. 4 is illustrated and described as being executed in sequence. However, the present invention is not limited to the illustrated order, and according to the present invention, some processes can be performed in a different order and / or simultaneously with processes different from those illustrated and described. Also, not all of the illustrated features are required to implement the method according to an aspect of the present invention.

[0030] FIG. 4 shows an example of a method 150 for measuring the scalar and vector components of an external magnetic field via a magnetometer system (e.g., atomic magnetometer system 10). At 152, a plurality of predetermined AC magnetic fields (e.g., magnetic fields B1 to B X ) are provided via a sensor cell (e.g., sensor cell 58) associated with a magnetometer (e.g., one of magnetometers 14). The sensor cell contains an alkali metal vapor. At 154, an optical probe beam (e.g., optical probe beam OPT PRB ) and an optical pump beam (e.g., optical pump beam OPT PMP ) pass through the sensor cell in pulses. At 156, a total magnetic field (e.g., total magnetic field B TOT ) including the external magnetic field and each of the plurality of predetermined AC magnetic fields is measured in response to the reception of a detection beam (e.g., detection beam OPT DET ) corresponding to the optical probe beam exiting the sensor cell. At 158, the total magnetic field is demodulated based on the plurality of predetermined AC magnetic fields to calculate the scalar and vector components of the external magnetic field.

[0031] The foregoing description is illustrative of the present invention. Although it is of course impossible to describe every conceivable combination of components or methods for the purpose of explaining the present invention, those skilled in the art will recognize that many additional combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the present application, including the appended claims. Also, when the present disclosure or claims enumerate an element as "one," "a first," or "another," or their equivalents, it should be construed to include one or more such elements, and is not intended to require or exclude two or more such elements. As used herein, the term "comprising" means including but not limited to. The term "based on" means based at least in part on. The technical idea included in the present disclosure is described below. (Appendix 1) A magnetometer, a sensor cell containing an alkali metal vapor, a magnetic field generator system configured to generate a plurality of predetermined AC magnetic fields through the sensor cell, a laser system configured to pulse-supplying an optical pumping beam and an optical probe beam through the sensor cell to promote the precession motion of the alkali metal vapor, and supplying a detection beam corresponding to the optical probe beam exiting the sensor cell, wherein the detection beam exhibits optical characteristics corresponding to the changed precession motion of the alkali metal vapor based on the plurality of predetermined AC magnetic fields and an external magnetic field, the laser system, a detection system configured to monitor the detection beam to detect the changed precession motion of the alkali metal vapor and calculate a scalar component and a vector component of the external magnetic field based on the plurality of predetermined AC magnetic fields, a magnetometer comprising the above. (Appendix 2) The magnetometer according to Appendix 1, wherein the laser system includes an optical coupler configured to axially couple the optical pumping beam and the optical probe beam to generate a combined beam guided through the sensor cell. (Appendix 3) The magnetometer according to Appendix 1, wherein the detection system is configured to measure a total magnetic field including the external magnetic field and the plurality of predetermined AC magnetic fields, and demodulate the total magnetic field by each of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field. (Appendix 4) The magnetometer according to Appendix 3, wherein each of the plurality of AC magnetic fields is provided at an individual frequency, and the detection system is configured to demodulate the total magnetic field by the individual frequency of each of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field. (Appendix 5) The magnetometer according to Appendix 3, wherein the plurality of predetermined AC magnetic fields are provided at a predetermined relative angle to each other in three-dimensional space, and the detection system is configured to demodulate the total magnetic field by each of the plurality of predetermined AC magnetic fields to determine the vector component of the external magnetic field with respect to the predetermined relative angle of the plurality of predetermined AC magnetic fields. (Appendix 6) The magnetometer according to Appendix 5, wherein the plurality of predetermined AC magnetic fields include three AC magnetic fields that are substantially orthogonal to each other. (Appendix 7) The detection system is configured to square the total magnetic field and demodulate the squared total magnetic field by first and second harmonics related to the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, the magnetometer according to appended claim 3. (Appended claim 8) The optical probe beam and the optical pump beam are supplied in pulses at a frequency corresponding to the precession frequency of the alkali metal vapor, the magnetometer according to appended claim 1. (Appended claim 9) A magnetometer system including the magnetometer according to appended claim 1 arranged in an array and including a plurality of magnetometers each configured to calculate the scalar component and the vector component of the external magnetic field, the magnetometer system further including a magnetic field tensor processor configured to calculate a magnetic field gradient related to the external magnetic field. (Appended claim 10) At least some of the plurality of magnetometers are arranged in a planar array, the magnetometer system according to appended claim 9. (Appended claim 11) At least one of the plurality of magnetometers is offset from the planar array to provide redundant calculations of the scalar component and the vector component of the external magnetic field, the magnetometer system according to appended claim 10. (Appended claim 12) A method for measuring the scalar component and the vector component of an external magnetic field via a magnetometer system, providing a plurality of predetermined AC magnetic fields through a sensor cell related to the magnetometer and including an alkali metal vapor, supplying an optical probe beam and an optical pump beam in pulses through the sensor cell, determining a total magnetic field including the external magnetic field and each of the plurality of predetermined AC magnetic fields in response to reception of a detection beam corresponding to the optical probe beam exiting the sensor cell, demodulating the total magnetic field based on the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, comprising the method. (Appended claim 13) Supplying the optical pump beam and the optical probe beam includes axially coupling the optical probe beam and the optical pump beam and supplying the coupled beam in pulses based on the precession frequency of the alkali metal vapor through the sensor cell, the method according to appended claim 12. (Appended claim 14) Supplying the plurality of predetermined AC magnetic fields includes supplying the plurality of predetermined AC magnetic fields at individual frequencies and at individual predetermined relative angles to each other in three-dimensional space, and the detection system is configured to demodulate the total magnetic field with respect to the individual predetermined relative angles by the individual frequencies of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, the method according to appended claim 12. (Appended claim 15) Further comprising squaring the total magnetic field, and demodulating the total magnetic field includes demodulating the squared total magnetic field with first and second harmonics related to the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, the method according to appended claim 12. (Appended claim 16) Determining the scalar component and the vector component of the external magnetic field via each of a plurality of magnetometers arranged in a planar array Determining a magnetic field gradient based on determining the scalar component and the vector component of the external magnetic field via each of a plurality of magnetometers The method according to appended claim 12, further comprising. (Appended claim 17) A magnetometer system, Comprising a plurality of magnetometers, each of the plurality of magnetometers A sensor cell containing an alkali metal vapor, A magnetic field generator system configured to generate a plurality of predetermined AC magnetic fields via the sensor cell, A laser system configured to pulse a light pump beam and a light probe beam via the sensor cell to promote the precession motion of the alkali metal vapor, and to supply a detection beam corresponding to the light probe beam exiting the sensor cell, wherein the detection beam exhibits optical characteristics corresponding to the changed precession motion of the alkali metal vapor based on the plurality of predetermined AC magnetic fields and the external magnetic field, the laser system, A detection system configured to monitor the detection beam to detect the changed precession motion of the alkali metal vapor and to calculate the scalar component and the vector component of the external magnetic field based on the plurality of predetermined AC magnetic fields, and the plurality of magnetometers including A magnetic field tensor processor configured to calculate a magnetic field gradient based on the scalar component and the vector component of the external magnetic field calculated by each of the plurality of magnetometers, A magnetometer system comprising. (Appended claim 18) Each of the plurality of predetermined AC magnetic fields is provided at an individual frequency and the plurality of predetermined AC magnetic fields are provided at a predetermined relative angle to each other in three-dimensional space, and the detection system of each of the plurality of magnetometers demodulates the total magnetic field with respect to the predetermined relative angle of the plurality of predetermined AC magnetic fields by the individual frequencies of each of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, the magnetometer system according to appended claim 17. (Appended claim 19) The detection system of each of the plurality of magnetometers is configured to square the total magnetic field and demodulate the squared total magnetic field by first and second harmonics related to the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field, the magnetometer system according to appended claim 17. (Appended claim 20) A part of the plurality of magnetometers is arranged in a planar array, and at least one of the plurality of magnetometers is offset from the planar array to provide redundant calculation of the scalar component and the vector component of the external magnetic field, the magnetometer system according to appended claim 17.

Claims

1. A magnetometer, comprising: A sensor cell containing an alkali metal vapor; A magnetic field generator system configured to generate a plurality of predetermined AC magnetic fields through the sensor cell; A laser system configured to pulse-supplying an optical pump beam and an optical probe beam through the sensor cell to promote the precession motion of the alkali metal vapor, and to supply a detection beam corresponding to the optical probe beam exiting the sensor cell, wherein the detection beam exhibits optical characteristics corresponding to the changed precession motion of the alkali metal vapor based on the plurality of predetermined AC magnetic fields and an external magnetic field; A detection system configured to monitor the detection beam to detect the changed precession motion of the alkali metal vapor and to measure the total magnetic field including the external magnetic field and the plurality of predetermined AC magnetic fields, and configured to square the measured total magnetic field and demodulate the measured and squared total magnetic field by first and second harmonics related to the plurality of predetermined AC magnetic fields to calculate a scalar component and a vector component of the external magnetic field based on the plurality of predetermined AC magnetic fields; A magnetometer comprising the above.

2. The magnetometer according to claim 1, wherein the laser system includes an optical coupler configured to axially couple the optical pump beam and the optical probe beam to generate a combined beam guided through the sensor cell.

3. The magnetometer according to claim 1, wherein each of the plurality of AC magnetic fields is provided at an individual frequency, and the detection system is configured to demodulate the total magnetic field by the individual frequencies of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field.

4. The plurality of predetermined AC magnetic fields are provided at a predetermined relative angle to each other in a three-dimensional space, and the detection system is configured to demodulate the total magnetic field by each of the plurality of predetermined AC magnetic fields and determine the vector components of the external magnetic field with respect to the predetermined relative angle of the plurality of predetermined AC magnetic fields. The magnetometer according to claim 1.

5. The magnetometer according to claim 4, wherein the plurality of predetermined AC magnetic fields include three AC magnetic fields that are substantially orthogonal to each other.

6. The magnetometer according to claim 1, wherein the optical probe beam and the optical pump beam are supplied in a pulsed manner at a frequency corresponding to the precession frequency of the alkali metal vapor.

7. A magnetometer system including a plurality of magnetometers according to claim 1, at least a part of the plurality of magnetometers being arranged in an array, and the plurality of magnetometers being configured to calculate the scalar component and the vector component of the external magnetic field respectively. A magnetometer system further comprising a magnetic field tensor processor configured to calculate a magnetic field gradient related to the external magnetic field.

8. The magnetometer system according to claim 7, wherein the array is a planar array, and at least one of the plurality of magnetometers is offset from the planar array to provide redundant calculation of the scalar component and the vector component of the external magnetic field.

9. A method for measuring a scalar component and a vector component of an external magnetic field via a magnetometer system, Providing a plurality of predetermined AC magnetic fields through a sensor cell related to the magnetometer and including an alkali metal vapor, Supplying an optical probe beam and an optical pump beam in a pulsed manner through the sensor cell, Determining a total magnetic field including the external magnetic field and each of the plurality of predetermined AC magnetic fields in response to receiving a detection beam corresponding to the optical probe beam exiting the sensor cell, Demodulating the total magnetic field based on the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field. A method comprising the steps of:

10. Supplying the optical pump beam and the optical probe beam includes axially coupling the optical probe beam and the optical pump beam and supplying the coupled beam through the sensor cell in a pulsed manner based on the precession frequency of the alkali metal vapor. The method according to claim 9.

11. Supplying the plurality of predetermined AC magnetic fields includes supplying the plurality of predetermined AC magnetic fields at individual frequencies and at individual predetermined relative angles to each other in three-dimensional space. The detection system is configured to demodulate the total magnetic field with respect to the individual predetermined relative angles by the individual frequencies of the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field. The method according to claim 9.

12. Further comprising squaring the total magnetic field, and demodulating the total magnetic field includes demodulating the squared total magnetic field by first and second harmonics related to the plurality of predetermined AC magnetic fields to calculate the scalar component and the vector component of the external magnetic field. The method according to claim 9.

13. Determining the scalar component and the vector component of the external magnetic field through each of a plurality of magnetometers arranged in a planar array. Determining a magnetic field gradient based on determining the scalar component and the vector component of the external magnetic field through each of the plurality of magnetometers. The method according to claim 9, further comprising the steps of:

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